Apex domains cannot have CNAME records.
Question and response
Question
dig sap.asia. NS
Answer
sap.asia. 5 NS ns4.sap.asia.
sap.asia. 5 NS ns2.sap.de.
sap.asia. 5 NS ns1.sap.net.
sap.asia. 5 NS ns3.sap.com.
Authority
The response has no authority records.
Additional
ns4.sap.asia. 5 A 169.145.112.153
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0